A low-light-level camera system is designed based on the scientific Complementary Metal Oxide Semiconductor(CMOS) image sensor LTN4625 in order to meet the requirements of the high resolution and high dynamic range low light imaging system. According to the readout structure characteristics of pixel of LTN4625,the FPGA is taken as the control core of the camera system and an image fusion algorithm based on tensor optimization is proposed. The dynamic range of the camera is extended effectively and the image quality is improved. The imaging test results show that the camera can output pictures at 50 fps and the resolution of image is 4 608×2 592. The dynamic range of image is improved to 54.7 dB from 5.2 dB for low gain data and 11.4 dB for high gain data. This design is a kind of low-light-level camera design method with high dynamic response range and good imaging effect under weak light environment.